This relates to the continuous casting of molten metals, and more particularly to the continuous casting of steel. In continuous casting, molten metal is generally poured from a ladle into an intermediate holding vessel known as a tundish. Both ladles and tundishes commonly have a nozzle in the bottom of the vessel through which the molten metal is poured. The receiving vessel is a water-cooled, open ended mold, which oscillates vertically during the pouring operation.
At the top of the mold, as presently configured, is a mold top flange, which is sometimes known as a top plate. This top flange is provided with a generally central opening through which molten metal is poured into the casting mold. During pouring, molten metal will splash onto the top flange where it solidifies, as the mold is cool in relation to the molten metal. A ragged pouring stream will also cause spatters of molten metal to adhere to the mold top flange. The solidified metal particles adhering to the mold top flange are known as "clingers". The opening at the top of the mold is reduced in area by the presence of clingers, which are removed by burning with an oxygen lance. The lance also damages the interior edges of the mold top flange, rendering it gouged and rough. The molten metal splash and spatter have an even greater tendency to adhere to the rough surfaces of the top flange than to the smooth surfaces of the top flange. The splash and spatter remain in place where they impact the top flange, rather than running down into the mold while still molten. Thus, the present solution to the problem of clingers on a continuous casting mold top flange of burning or melting them with an oxygen lance actually contributes to the problem.
After about 150 to 200 heats of steel have been cast through a mold top flange, the interior edges of the casting opening in the top flange becomes so rough that the top flange must be removed from service and rebuilt.
The currently practiced rebuilding procedure is to build up the surface of the top flange to beyond its original configuration by adding weld metal, then to machine the flange to its original dimensions. Large steel mills have a machine shop on the premises to handle this procedure, but most of the small mills and the newer mini-mills have the repair made by an independent-contractor, thereby incurring substantial costs, including shipping costs.